Don’t worry. Your eyeballs are safe, though those around might suffer the collateral damage. That tickle in your nose turns into a tsunami that releases 100,000 germs in the air.

“It’s a vector for transmitting infections, colds and spread of other particles,” said Everett Clinic allergist Dr. Brett Buchmiller.

For the sneezer, sneezing is a good thing.

“Your sneeze is mostly a protective reflex,” Buchmiller said. “It clears secretions and any debris that might be in there.”

A sneeze is a sternutation, a convulsive expulsion of air from the lungs through the nose and mouth when nerve endings get irritated.

Sneezing is a normal function for creatures both warm-blooded and scaly.

Iguanas are the sneeziest critters on the planet. Sneezing allows the lizards to detoxify from excess salts in the body.

Lizards do it without missing a beat, unlike humans, whose faces contort like Picasso portraits.

A trigger or substance sets off the brain’s sneeze center. There’s no stopping it when that tickle in your nose flips the gears into full eruption of a rapid chain of events.

The spasm clenches the face. Eyes close. Throat muscles relax. Saliva and mucus are forced out of your mouth and nose, ideally into a tissue or the crook of your elbow.

Pressure behind the eyes may increase slightly, but not enough to propel your eyeballs out of their sockets.

“It can make your heart slow down,” Buchmiller said.

It won’t kill you, in itself. An ill-timed sneeze while driving could make you miss seeing a car in front of you or a light change.

Reaching for a tissue can also distract drivers.

At least in a car, you can sneeze in private.

People ignore a cough but seem compelled to cap a sneeze with something. Sneezing is often followed by an equally funny sound, “Gesundheit,” wishing good health in German.

“Bless you” started in the 14th century during the time of the plague when it was thought it was a good way to ward off diseases.

The Greeks and Romans regarded sneezing as a sign of wellness, responding with “Live long” or “May Jupiter bless you.”

There’s folklore that every time you go achoo, someone somewhere is thinking of you. Or gossiping about you, depending on the country of origin.

Two sneezes in a row means something bad is being said. Three sneezes means it’s really bad.

Some people sneeze more than others.

For those with allergies, sneezes can be decreased with antihistamines or shots or getting rid of the cat.

There’s lots of stuff to sneeze about.

Irritation. Plucking eyebrows and nose hairs.

Some people sneeze from bright sunlight. Pepper is another culprit.

It can be psychogenic, all in your mind. “They get it in their head that something is always irritating it even if it isn’t,” Buchmiller said. “It’s rare.”

Exercise can trigger a sneeze, but that’s no excuse to avoid it.

An overly full stomach can solicit a sneeze, and there’s even a name for it: snatiation. It’s a medical disorder characterized by uncontrollable bursts of sneezing brought on by fullness of the stomach.

Sexual orgasm can stimulate a sneeze.

“It’s not a common problem,” Buchmiller said, “but it can happen.”

That might call for a double “bless you.”

Strange sneezes

The longest sneezing spree, according to common lore: 978 days, a record set by Donna Griffiths, 12, of Worcestershire, England, in the early 1980s.

Unless you’re little Donna, you don’t sneeze in your sleep. When you sleep, so do your sneezing nerves.

How do you stop a sneeze? Breathe through your mouth and pinch the end of your nose. It’s not foolproof.

The nickname for sneezing in bright light is ACHOO, an acronym for Autosomal Dominant Compelling Helio-Ophthalmic Outburst syndrome.

“Fred Ott’s Sneeze,” also known as “Edison Kinetoscopic Record of a Sneeze,” is an 1894 black-and-white silent film shot in 1894 and the first motion picture to be copyrighted in the U.S.

In the 5-second film, one of Thomas Edison’s assistants, Fred Ott, takes a pinch of snuff and sneezes. Movie audiences were easy to please back then.